javax.mail.MessagingException：无法连接到 SMTP 主机 [重复]

Question

可能重复：
javax.mail.MessagingException: Could not connect to SMTP host: smtp.gmail.com, port: 25;

我尝试通过 jsp 页面发送电子邮件，但显示以下错误：

javax.mail.MessagingException：无法连接到 SMTP 主机：www.gmail.com，端口：25，响应：421

这是我用来发送电子邮件的代码：

<%
    try
    {
        String host = "www.gmail.com";
        String to = request.getParameter("to");
        String from = request.getParameter("from");
        String subject = request.getParameter("subject");
        String messageText = request.getParameter("body");
        boolean sessionDebug = false;

        Properties props = System.getProperties();
        props.put("mail.host", host);
        props.put("mail.transport.protocol", "smtp");
        Session mailSession = Session.getDefaultInstance(props, null);

        mailSession.setDebug(sessionDebug);

        Message msg = new MimeMessage(mailSession);
        msg.setFrom(new InternetAddress(from));
        InternetAddress[] address = {new InternetAddress(to)};
        msg.setRecipients(Message.RecipientType.TO, address);
        msg.setSubject(subject);
        msg.setSentDate(new Date());
        msg.setText(messageText);

        Transport.send(msg);
        out.println("Mail was sent to " + to);
        out.println(" from " + from);
        out.println(" using host " + host + ".");
    }
    catch (MessagingException mex) 
    {
        System.out.println("Error: unable to send message....");
        mex.printStackTrace();
    }
%>

谁能告诉我是什么导致了这个错误？

Answer 1

您需要指向 gmail 邮件服务器，而不是 Web 服务器。

所以改变

String host = "www.gmail.com";

到

String host = "smtp.gmail.com";

编辑：您还需要：String port = "587"; 而不是 ...port = "25"